Method of making a plasma display panel

ABSTRACT

A plasma display panel comprising first and second transparent substrates, each having a plurality of spaced parallel conductors on a first surface thereof, and a plurality of spaced, parallel grooves in a second, opposed, surface thereof, with the grooves being aligned with associated conductors on the same substrate. The substrates are assembled with their second surfaces together and with the grooves of the first substrate being positioned at an angle to the grooves of the second substrate so as to form cells at crossover points of the grooves. The grooves of the first and second substrates are made by using the associated conductors as masks to produce self-compensated alignment between conductors and grooves. An electroluminescent material is contained within the grooves.

United States Patent Coleman NIETHOD OF MAKING A PLASMA DISPLAY PANEL [72] Inventor: William E. Coleman, Dayton, Ohio [73] Assignee: The National .Cash Register 'Company, Dayton, Ohio [22] Filed: May 3, 1971 [21] Appl. No.: 139,750

Related US. Application Data [62] Division of Ser. No. 823,408, May 9, 1969,

[ Nov. 28, 1972.

3,497,751 2/1970 Cullis ..3l3/l08 R Primary Examiner-John F. Campbell Assistant Examine'rW. Tupman Attorney-Louis A. Kline, Albert L. Sessler, Jr. and Elmer Wargo [57] ABSTRACT A plasma display panel comprising first and second transparent substrates, each having a plurality of spaced parallel conductors on a first surface thereof, and a plurality of spaced, parallel grooves in a second, opposed, surface thereof, with the grooves being aligned with associated conductors on the same substrate. The substrates are assembled with their second surfaces together and with the grooves of the first substrate being positioned at an angle to the grooves of the second substrate so as to form cells at crossover points of the grooves. The grooves of the first and second substrates are made by using the associated conductors as masks to produce self-compensated alignment between conductors and grooves. An electroluminescent material is contained within the grooves.

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INVENTOR WILLIAM E. COLEMAN 0% Vi BY I 1%" 7 w fr HIS ATTORNEYS METHODOF MAKING A PLASMA DISPLAY I PANEL CROSS REFERENCE TO RELATED APPLICATION This application is a division of U.S. Pat. application Ser. No. 823,408,'filed on May 9, 1969, by the same inventor as the present application and now abandoned.

BACKGROUND OF THE INVENTION This invention relates to a method of making a plasma display panel.

One form of an electroluminescent display device consists of an electroluminescent film or layer having first and second mutually orthogonal arrays of parallel, separated electrical conductors positioned on each side thereof to form a crossed-grid structure. When a suitable voltage is applied between a selected conductor of the first array and a selected conductor of the second array, the portion of the electroluminescent layer at the intersection of the selected conductors will glow.

Another form of an electroluminescent display panel consists of first and second thin substrates with each having a plurality of spaced, parallel conductors thereon. The panel also includes a third substrate sandwiched between the first and second substrates with the conductors of the first substrate being perpendicular to the conductors of the second substrate, producing a plurality of crossover points. The third substrate has a plurality of holes therein, one hole being provided for each crossover point, and an electroluminescent material being present in each hole. Because-the individual substrates are very thin, they are very fragile and tend to break when handled. Placing one hole in the third substrate at each crossover point presents alignment problems when the panel is being fabricated.

in contrast with the above, applicants display panel has self-compensated alignment due to each conductor located on one surface of a substrate being used as a mask to produce a groove located on the opposite surface of the substrate. Applicants novel panel is inexpensive to manufacture in both planar and curved sections in various geometric configurations.

SUMMARY OF THE INVENTION This invention relates to a plasma display panel which comprises first and second transparent substrates, each substrate having first and second opposed surfaces. The first surface of each substrate has a plurality of spaced, parallel conductors thereon, and the second surface of each substrate has a plurality of spaced, parallel grooves therein, each groove being located in opposed, aligned relation with an associated conductor on the opposed surface of the substrate.

The first and second substrates are assembled with their second faces contacting each other and with the conductors of the first substrate being at an angle to the conductors of the second substrate to form a plurality of crossover points. Because the grooves of each substrate are aligned with the associated conductors, the grooves of the first substrate cross the grooves of the second substrate to form a cell at each of the crossover points of the related conductors. An electroluminescent material fills the grooves of both substrates and may be sealed therein if necessary.

The grooves of each substrate are formed by using the conductors onthe opposed surface of the substrate as a mask, thereby providing self-compensated alignment between conductor and grooves.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a general view, in perspective, andpartly in cross section, of a plasma display panel of this invention, showing the formation of gas cells or chambers therein and the location of thespaced parallel conductors.

FIG. 2 is a plan view of one side of the panel shown in FIG. 1.

FIG. 3 is a cross-sectional view through one substrate, showing the conductors on one surface thereof, which conductors are used as a mask for forming the grooves on the opposed surface thereof. I

FIG. 4 is a view similar to FIG. 3, showing the grooves as formed.

- FIG. 5 is an elevational view taken from direction A of FIG. 1, showing more details of the display panel.

"FIG. 6 is a cross-sectional view in elevation of a portion of a substrate'of asecond embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIGS. 1, 2 and 5 show a plasma display panel 10 of this invention. The panel 10 includes a first substrate 12, which is made of a transparent material, like glass, and a second substrate 14, which is made of the same material.

The first substrate "12 has a plurality of spaced, thin, flat electrical conductors 16 in spaced, parallel relationship on a first surface 18 thereof. Similarly, the second substrate 14 has a plurality of spaced, thin, flat electrical conductors 20 in parallel relationship on a first surface 22 thereof. The conductors 16 and 20 in one embodiment of the invention are made of gold.

The first substrate 12 has a second surface 24, in which a plurality of grooves 26 are formed. The grooves 26 are arranged in spaced parallel relationship with one another, and each groove 26 is aligned with a conductor 16 on the opposed surface 18 of the substrate 12. The grooves 26 have a trapezoidal shape in cross-section, with the'non-parallel sides thereof converging towards the associated conductors. The second substrate 14 is identical'in construction to the first substrate 12, and it has av plurality of grooves 28 located on a second surface 30 thereof.

The first and second substrates 12 and 14, respectively, are assembled together, as is best shown in FIGS. 1 and 5. These substrates are assembled together so that the second surfaces 24 and 30 thereof are contacting each other, and the grooves 26 of the first substrate 12 are perpendicular to the, grooves 28 of the second substrate 14, so that cells (like the cell 32) form at the crossover points. These cells 32 are located between the crossover points of the conductors 16 of the'first substrate 12 and the conductors 20 of the second substrate 14. Each of these conductors has a terminal conductor (like 34) secured thereto for placing an electrical potentialacross selected conductors 16 and 20 of the first and second substrates 12 and 14, respectively, when the display panel 10 is to be used.

The assembled substrates l2 and 14 (FIG. 1) have their edges sealed by a layer of fused glass 36, which extends completely around the perimeters of the substrates. After the edges aresealed, the air within the grooves 26 and 28 is vacated via a conduit 38 communicating with the interior of one of the grooves v 28. After the interior of the display panel is vacated of air, the grooves 26 and 28 are filled via the conduit 38 with an electroluminescent material, and the conduit is thereafter sealed over. The material which fills the grooves may be a gas at one sixth to five sixths at atmospheric pressure, which gas is a conventional mixture of neon, helium, and nitrogen. As used herein, the term electroluminescent materia is defined as meaning any material which may be excited to lurninesce by the application of an electrical field thereacross, and a suitable material in other than gaseous form may be employed if desired.

To use the display panel 10 shown principally in FIG. 1, an electrical potential is placedon selected conductors 16 and of the first and second substrates 12 and 14, respectively, causing the gas Within the individual gas cells 32 located at the crossover points of the selected conductors to glow. In the embodiment shown in FIG. 1, a five-by-seven matrix of gas cells 32 is sufficient to provide an adequate definition of each character to be formed by the glowing cells. Even though the conductors 16 and 20 are opaque, a sufficient glow is visible at the crossover points of the cells due to the grooves (26, 28) having a width at the mouth thereof which width is wider than the width of the pertaining conductors 16 and 20. In a second embodiment of the invention, the conductors 16 and 20 are made of a transparent electrical conductor material like tin ox ide. The first and second substrates 12 and 14 could be curved sections instead of planar sections as shown. Also, while the two sets of conductors and corresponding grooves of the two substrates are shown in the drawings as being perpendicular to each other, it is contemplated that they could be positioned in any other angular relation, so long as this results in the desired sets of intersections.

The methods for making the substrates 12 and 14 can be best explained in conjunction with FIGS. 3 and 4. In one method, the substrate 12 has opaque electrical conductors l6 deposited on the first surface 18 in spaced, parallel relationship by conventional photoresist and metal deposition techniques. After the conductors 16 are deposited, a layer of photoresist 40 is deposited on the second surface 24 of the substrate 12. While the conductors 16 are being used as a mask, the photoresist layer 40 is exposed. Those areas, like 42 (FIG. 3), which are directly behind the conductors 16 when exposing, are removed conventionally to expose the second surface 24 of the substrate. The areas 42 are then etched conventionally to produce the grooves 26 as shown in FIG. 4. In the embodiment shown, the substrate 12 has a thickness of about 0.012 inch, and the depth of the grooves 26 is about 0.008 inch. The second substrate 14 is made the same way as the first substrate 12, and the two are assembled as shown in FIG. 1, as previously explained. a

An alternate method for producing the display panel 10, in which the electrical conductors 16 and 20 are transparent, is generally the same as that already described in relation to FIGS. 3 and 4, with one general difference. Because the conductors 16 and 20 are used as masks, it is necessary to place an opaque layer of material over these conductors prior to their being used as masls.

The alternate method may be performed as follows. A layer of tin oxide which is transparent is deposited over the first surface 42 of the substrate 44 (FIG. 6), and a layer of chromium is vacuum deposited thereover. By use of conventional photoresist and etching techniques, a layer of chromium 46 is left on each of the conductors 48 which are formed from the layer of tin oxide. With the structure shown in FIG. 6, the conductors 48 with the layer of chromium 46 thereon may be used to produce the grooves (similar to the grooves 26 in FIG. 5) in thesecond surface 50 of the substrate 44 according to the techniques already described in relation to FIGS. 3 and 4. After the grooves are formed in the second surface 50, the layer of chromium 46 is removed from each of the transparent conductors 48, and a display panel, similar to that shown in FIG. 1, may then be formed as shown therein; With the transparent conductors 48, more light is viewable at the gas cells 32 (FIG. 1), making the characters produced by a matrix of the cells more clearly defined.

What is claimed is:

1. The method of producing a plasma display panel comprising the steps of:

a. forming a plurality of spaced, parallel conductors on a first surface of a transparent substrate having first and second opposed surfaces;

b. depositing a layer of photoresist material on the second surface of said substrate;

c. exposing said photoresist while using said conductors as a mask;

d. removing the unexposed photoresist and forming grooves in those areas from which the photoresist was removed;

e. assembling two of said substrates as obtained from the previous step (d) so that the second surfaces thereof are facing each other with the grooves of the first of the two substrates being at an angle with relation to the grooves of the second of said substrates;

f. joining said two substrates together; and

g. filling said grooves with an electroluminescent material.

2. The method as claimed in claim 1 in which said step of forming grooves (step d) is an etching step which produces grooves which are tapered in cross section. I

3. The method as claimed in claim 1 in which said step (f) of joining said two substrates includes a sealing operation to make the assembly formed thereby airtight.

4. The method of producing a plasma display panel comprising the steps of:

a. forming a plurality of spaced, parallel transparent conductors, each having an opaque layer of material thereon, on a first surface of a substrate having first and second opposed surfaces;

d. depositing a layer of photoresist material on the second surface of said substrate;

. exposing said photoresist material while using said conductors with the opaque layer of material thereon as a mask;

. removing the unexposed photoresist and forming grooves in those areas from which the photoresist was removed;

removing said opaque layer of material; assembling two of said substrates as obtained from the previous step (e) so that the second surfaces 

1. The method of producing a plasma display panel comprising the steps of: a. forming a plurality of spaced, parallel conductors on a first surface of a transparent substrate having first and second opposed surfaces; b. depositing a layer of photoresist material on the second surface of said substrate; c. exposing said photoresist while using said conductors as a mask; d. removing the unexposed photoresist and forming grooves in those areas from which the photoresist was removed; e. assembling two of said substrates as obtained from the previous step (d) so that the second surfaces thereof are facing each other with the grooves of the first of the two substrates being at an angle with relation to the grooves of the second of said substrates; f. joining said two substrates together; and g. filling said grooves with an electroluminescent material.
 2. The method as claimed in claim 1 in which said step of forming grooves (step d) is an etching step which produces grooves which are tapered in cross section.
 3. The method as claimed in claim 1 in which said step (f) of joining said two substrates includes a sealing operation to make the assembly formed thereby airtight.
 4. The method of producing a plasma display panel comprising the steps of: a. forming a plurality of spaced, parallel transparent conductors, each having an opaque layer of material thereon, on a first surface of a substrate having first and second opposed surfaces; d. depositing a layer of photoresist material on the second surface of said substrate; c. exposing said photoresist material while using said conductors with the opaque layer of material thereon as a mask; d. removing the unexposed photoresist and forming grooves in those areas from which the photoresist was removed; e. removing said opaque layer of material; f. assembling two of said substrates as obtained from the previous step (e) so that the second surfaces thereof are facing each other with the grooves of the first of the two substrates being at an angle to the groove of the second of said substrates; g. sealing said two substrates so as to make the assembly formed thereby airtight; and h. filling said grooves with an electroluminescent material. 